Effects of extremely low-frequency electric fields at different intensities and exposure durations on mismatch negativity

• Effects of ELF-EFs on ERPs depend on the dosage and duration of exposure.
• Four-week exposure to ELF-EF with an intensity of 18-kV/m affects auditory processing.
• Lipid peroxidation might have a role in the ELF-EF effects on auditory processing.
• Adaptive changes may occur to counteract free-radical effects of ELF-EF.

The effects of extremely low-frequency electric fields (ELF-EFs, 3–300 Hz) on lipid peroxidation levels and antioxidant enzyme activities have been shown in many tissues and plasma after exposure to 50-Hz alternating current (AC) electric fields. However, similar studies investigating brain lipid peroxidation status are limited. Moreover and as far as we know, no study has been conducted to examine mismatch negativity (MMN) response in rats following exposure to a 50-Hz AC electric field. Therefore, the purpose of the study was to investigate different intensities and exposure durations of ELF-EFs on MMN component of event-related potentials (ERPs) as well as apoptosis and oxidative brain damage in rats. Ninety male rats, aged 3 months were used in our study. A total of six groups, composed of 15 animals each, was formed as follows: sham-exposed rats for 2 weeks (C2), sham-exposed rats for 4 weeks (C4), rats exposed to 12-kV/m and 18-kV/m electric fields for 2 weeks (E12-2 and E18-2), rats exposed to 12- and 18-kV/m electric fields for 4 weeks (E12-4 and E18-4). At the end of the experimental period, MMN responses were recorded in urethane-anesthetized rats by electrodes positioned stereotaxically to the surface of the dura. After MMN recordings, animals were killed by exsanguination and their brain tissues were removed for 4-hydroxy-2-nonenal (4-HNE), protein carbonyl and TUNEL analysis. In the current study, different change patterns in ERP parameters were observed dependent on the intensity and exposure duration of ELF-EFs. There were differences in the amplitudes of ERP between the responses to the standard and the deviant tones in all groups. When peak-to-peak amplitude of the difference curves was evaluated, MMN amplitude was significantly decreased in the E18-4 group compared with the C4 group. Additionally, the amount of 4-HNE was increased in all experimental groups compared with the control group. Consequently, it could be concluded that electric field decreased MMN amplitudes possibly induced by lipid peroxidation.